This application is directed to substrate heating apparatus within the preferred embodiment of Chemical Vapor Deposition (CVD) apparatus and more specifically to an arrangement for supporting the heater filament of a deposition reactor.
Chemical Vapor Deposition (CVD) systems are widely used to deposit elemental, mixed phase and compound films in the manufacture of electronic devices, such as integrated circuits formed by the sequential or simultaneous deposition of compounds upon a heated substrate, which is usually in the form of a wafer that is typically mounted on a “susceptor” which may or may not rotate. The reactants are transported to the surface of the substrate, in the gas phase, by typically one or more carrier gases. The elements deposit on the wafer surface, forming the desired compound and any undesirable by-products are pumped away in a gaseous form. A heating element (filament) is mounted below the susceptor and heats the wafers. It is desirable to have the filament close to the susceptor to minimize power loses.
The filament of the heater assembly is subject to a number of problems which can lead to damage or failure, among these problems are: 1) warpage (into and out of its plane; such warping can cause the filament to contact the fixed or rotating susceptor leading to damage to the susceptor and filament 2) temperature asymmetries across the wafer and/or hardware (differential thermal expansion as it heats and cools or where different zones experience different values of heat loss leading to different local temperatures) 3) differing temperatures along the coils (where different zones experience different values of heat loss leading to different local temperatures) 4) lateral expansion which can cause adjacent coils to short out which can lead to catastrophic failure of the filament 5) reactivity with the process environment including reactivity with supporting elements such as insulators 6) fatigue wherein aging embrittlement leads to cracking failure in unsupported filaments (which are subject to general process system induced vibrations), among others. The problems are exacerbated by the increasing temperatures that are used in many advanced deposition methodologies.
The present invention is directed to apparatus for supporting the heater filament of the reactor in Chemical Vapor Deposition (CVD) system. The apparatus includes a recess or aperture disposed in a filament support plate; a rod is joined to at least one of the coils of the filament, and extends into the recess or aperture in the support plate. A thermally insulating sleeve surrounds the rod. The post and sleeve arrangement provide a controlled and adjustable amount of lateral and vertical movement to the rod and filament to prevent damage to the filament caused by thermal expansion while providing lateral and vertical support to the filament.